Not much is known about his beginning other than he was found on Mustafar as a teenager. He had constructed a lightsaber himself and was skilled with it and the force. It is yet to be explained why exactly either were with him. When he was brought to the temple, Jedi Master Saesee Tinn took him as an apprentice.The two fought in many battles together. But it took little time for the young Jedi to be knighted. He just as quickly became a decorated general.
Soon after becoming a general he was seduced to the dark side and procalimed himself Darth Phantom. He was then pulled out by a young female jedi, and returned to general status. He had seemingly aged after leaving the dark side, and became a High General of the Republic.
When Order Sixty-Six was called out, he and his elite men fell victim to the intial attack but escaped. He went into exile on Nar Shadda, taking up the job of bodyguard for hire. When the Empire finally caught him, they took advantage of his extrexme durability and tested many evil things on him. One such thing began to mutate him into a wampa like creature. He devolped technology to counter the mutation, but could never be fully rid of it.
When the New Jedi Order began, he returned to the Jedi as a High Jedi Master. He went on as such until, during meditation, an assassination attempt occured. He became one with the Force so as not to be killed. The assassin, Boba Fett, was caught soon there after, trying to flee the temple.
More on Master Phantom coming soon....